A PROTON-CYCLOTRON WAVE STORM GENERATED BY UNSTABLE PROTON DISTRIBUTION FUNCTIONS IN THE SOLAR WIND

R. T. Wicks, R. L. Alexander, M. Stevens, L. B. Wilson III, P. S. Moya, A. Vinas, L. K. Jian, D. A. Roberts, S. O'Modhrain, J. A. Gilbert, T. H. Zurbuchen

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

We use audification of 0.092 s cadence magnetometer data from the Wind spacecraft to identify waves with amplitudes $\gt 0.1$ nT near the ion gyrofrequency (~0.1 Hz) with duration longer than 1 hr during 2008. We present one of the most common types of event for a case study and find it to be a proton-cyclotron wave storm, coinciding with highly radial magnetic field and a suprathermal proton beam close in density to the core distribution itself. Using linear Vlasov analysis, we conclude that the long-duration, large-amplitude waves are generated by the instability of the proton distribution function. The origin of the beam is unknown, but the radial field period is found in the trailing edge of a fast solar wind stream and resembles other events thought to be caused by magnetic field footpoint motion or interchange reconnection between coronal holes and closed field lines in the corona.
Original languageEnglish
Pages (from-to)6-16
Number of pages9
JournalAstrophysical Journal
Volume819
Issue number1
Early online date23 Feb 2016
DOIs
Publication statusPublished - Feb 2016
Externally publishedYes

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